Hypertension, or high blood pressure, refers to a transitory or sustained elevation of systemic arterial blood pressure to a level that is likely to induce cardiovascular damage or other adverse consequences. Hypertension has been arbitrarily defined as a systolic blood pressure above 140 mmHg or a diastolic blood pressure above 90 mmHg. For patients suffering from hypertension, the long term mortality as well as the quality of life can be improved if blood pressure can be reduced. However, many hypertension patients may not respond to treatments related to lifestyle changes or anti-hypertension drugs. Consequences of uncontrolled hypertension include, but are not limited to, retinal vascular disease and stroke, left ventricular hypertrophy, heart failure, myocardial infarction, dissecting aneurysm, and endovascular disease. Therefore, there is a need for controlling blood pressure in these patients.